first night 
noun
The first public performance of a play or show: tickets for the first night sold out fast [as modifier]: some of the numbers appeared to be under-rehearsed, but maybe they were suffering first-night nerves...
- Occasional first-night glitches were far outweighed by the spirit of the acting.
- We were invited to the first-night party, but were both tired.
- The adult first-night audience of Peter Pan, told to clap if they believed in fairies, applauded thunderously: it was the birth of modern escapist entertainment.